Abstract: There is provided mechanisms for differential protection of a transmission line (20) of a transmission system (25). A method comprises obtaining a restraining current and a differential current from the transmission line (S102). The method comprises determining a compensation current for the differential current (S104). The method comprises providing the differential current as compensated for by the compensation current and the restraining current to a differential protection arrangement for making a trip decision (S106). The method comprises detecting an internal fault for the transmission system (S108). The method comprises, as a result thereof, providing the differential current without being compensated for by the compensation current and the restraining current to the differential protection arrangement for making the trip decision (S110).

Abstract: There is provided mechanisms for differential protection of a transmission line (20) of a transmission system (25). A method comprises obtaining a restraining current and a differential current from the transmission line (S102). The method comprises determining a compensation current for the differential current (S104). The method comprises providing the differential current as compensated for by the compensation current and the restraining current to a differential protection arrangement for making a trip decision (S106). The method comprises detecting an internal fault for the transmission system (S108). The method comprises, as a result thereof, providing the differential current without being compensated for by the compensation current and the restraining current to the differential protection arrangement for making the trip decision (S110).

Abstract: A method of current differential protection performed in a control device is disclosed, wherein the control device has a first operate-restrain characteristic with a differential characteristic pick-up setting ID. The method includes: determining currents of all terminals of a protected object; determining a differential current based on the determined currents; determining direct current, DC, components in the respective determined currents; detecting a fault; and adjusting, for a detected external fault, the operate-restrain characteristics by setting an adjusted differential characteristic pick-up setting ID_adj to be equal to the sum of the differential characteristic pick-up setting ID and the determined DC components, providing an adapted operate-restrain characteristics. Corresponding control device, computer program and computer program product are also disclosed.

Abstract: A method of current differential protection performed in a control device is disclosed, wherein the control device has a first operate-restrain characteristic with a differential characteristic pick-up setting ID. The method includes: determining currents of all terminals of a protected object; determining a differential current based on the determined currents; determining direct current, DC, components in the respective determined currents; detecting a fault; and adjusting, for a detected external fault, the operate-restrain characteristics by setting an adjusted differential characteristic pick-up setting ID_adj to be equal to the sum of the differential characteristic pick-up setting ID and the determined DC components, providing an adapted operate-restrain characteristics. Corresponding control device, computer program and computer program product are also disclosed.

Abstract: The present invention discloses a method for detecting a fault and a current differential protection system thereof. The method for detecting fault includes calculating fault component currents, calculating an operate current and a restraint current of all terminals, and adjusting an operate level by adapting an operate-restraint characteristic according to a fault component. The method has very small operating area for external faults, which makes the method very reliable even for the case with serious CT saturation. A very big operating area for internal faults makes the method very sensitive for internal faults even for a heavy load and high resistance fault.

Abstract: The present invention discloses a method for detecting a fault and a current differential protection system thereof. The method for detecting fault includes calculating fault component currents, calculating an operate current and a restraint current of all terminals, and adjusting an operate level by adapting an operate-restraint characteristic according to a fault component. The method has very small operating area for external faults, which makes the method very reliable even for the case with serious CT saturation. A very big operating area for internal faults makes the method very sensitive for internal faults even for a heavy load and high resistance fault.